Grinding machine



Oct. ll, 1932.

R. N. HEALD ET AL GRINDING MACHINE Original'Filed Jan. '24, .1925

6 Sheets-Sheet l nvamtoz d so W, um@ s@ Nap@ A R HG f 06t- 11, 1932 R.N. HEALD ETAL 1,881,553

GRINDING MACHINE Original Filed Jan. 24, 1925 6 Sheets-Sheet 2 anne/ufo@Ro er- NHecLEcL Wo. I GulRd. Hejrved F. Burns Geowno attenua? Oct. 11,1932. R1 N-||EALD ET AL 1,881,553

GRINDING MACHINE y,

6 Sheets-Sheet '3 Original Filed Jan. 24, 1925 gwvanoz RO er` N.Tfeclfcl. QOQSEdDJ GLLLECL Hl. recl. F! Burns o e. E Gcu'rLo Oct. 1l,1932. R, N HEALD ET AL 1,881,553

- GRINDING MACHINE Original Filed Jan. 24, 1925 6 Sheets-Sheet 4 ,agi lF 7 fr@ o (g1/wanton Roger* N. Hengel. wcLEcLo J'. GLLLBCL H red. RBLLr-ns 53 ff/5% we maar? Oct. 11, 1932. R. N. HEALD ET AL GRINDINGMACHINE Original Filed Jan. 24, 1925 6 Sheets-Sheet 5 nvednoz R N. Treueoeo :IGLLLEcL fleshed F! Burns George E. cLrrz o1. ug I l b 1i, 1.932.R, N, HEALD E1- AL 1,881,553-

GRINDING MACHINE Original Filed Jan. 24, 1925 6 Sheets-Sheet 6 "IIIlvwenoz Roger N. fecxEcL (IOCLPCLD I G LLPd.

Hegred. P. Burns.

Patented. oct.' 11, 1932 UNITED STATES PATENTl OFFICE ROGER N. HEALD,WALDO J. GUILD, ALFRED Il?. BURNS, AND GEORGE E. GARNO, F WORCESTER,MASSACHUSETTS,2ASSIGNOBS TO THE HEALD MACHINE COMPANY, 0F WORCESTER,MASSACHUSETTS, A CORPORATION 0F MASSACHUSETTS GRINDING MACHINE Original'application filed January 24, 1925, Serial No. 4,466. Divided and thisapplication filed April 13,

1927. Serial No. 183,504.

Thist invention `relates to grinding machincs,-the present applicationbeing a division of parent application Serial No. 4,466, filed January24, 1925, and issued as United States Letters Patent No. 1,751,202,dated March 18, 1930. The latter relates toan automatic grinding machineprovided lwith a work contacting calipering or gauging mechanism andmeans set in operation thereby to cause the grinding Wheel to be dressedand trued at a certain stage in the grinding operation, andv means alsoset in operation by the calipering mechanism to terminate the grindingwhen the workpiece reaches the eX- act desired size. The presentinvention relates to the calipering mechanism of and by itself,including the instrumentalities for causing it to swing into andout ofthe workpiece at the commencement and termination respectively, of thegrinding operation.

The machine of our invention is adapted for the rapid production ofarticles suchv as sleeves, gears,vbushings, ball races andthe like,whose internal surfaces must be ground i to close limits. The presentapplication relates in detail only to the calipering mechanism, and sofar as the rest of the mechanism and machine movements which qualify theyaction thereof is concerned, any equivalentl may be substituted.

The construction and Loperation of said calipering mechanism will morefully appear from thc' following description, taken in connection withthe accompanying drawings, in which K l Fig. 1 isa front elevation of agrinding, machine embodying the invention.

Figs. 2 and 3 are, respectively, a front elevation and a plan view,showing the wheel dressing operation.

Figs. 4 and 5 are, respectively, a front elevation and a plan View,showing the positions automatically assumedby thefparts at the finish ofcach grinding operation.

Fig. 6 is a fragmentary plan view, on a enlarged scale, of the workgauging device and its associated parts.

Fig. 7 is ay side view of the parts shown in Fig.

Fig. 8 is a detached rear view of the mechanism shown in Figs. 6 and 7.

Fig. 9 isa sectional view on the line 9-9 of Fig. 6.

Fig. 10 is a sectional view on the line 10-10 of Fig. 6.

Fig. 11 is a wiring diagram. f Like reference characters refer to likeparts in the different figures. Referring to the drawings, particularlyFigs. 1 to 5 inclusive, the machine provides the usual reciprocatorytable or carriage 1, which is ordinarily provided in any internalgrinding machine. In such a machine, either the grinding wheel or thework to be ground may be carried on the table 1, the reciprocations ofthe latter being utilized in' either case to produce a relativetraversing movement between the grinding wheel and the work. As hereshown, the ta'ble 1 supports and carries a wheel head 2 of the usualconstruction,-while the work which is to be operated upon is held in awork head 3, the latter being carried by a bridge 4 which spans theslideways providedv by the machine frame for the back and forth movementof the table 1.

Said back and forth movement ofthe table 1, to cause the rotatinggrindingwheel 5 to make the required interior traverse of the rotatingworkpiece 6, may be imparted in any well known manner, as for instance,by the use of the fluid pressure controlling and reversing mechanismwhich forms the subject matter of United States Letters Patent No.1,582,468 to Heald and Guild, granted April 27, 1926. Such mechanism, orits equivalent, forms no part of the present invention and a detaileddescription thereof is therefore unnecessary; it is sufcient to note,for the purposes of the present application, that the driving meansemployed'for the reciprocation of the table 1, be it hydraulic drive, orgear drive, or any other type, procures the reversal of said table ateach end of the latters normal-working stroke, by the use of spacedadjustable dogs 7 and 8, carried by the table and adapted to alternatelyengage and -move an interposed member 9,

' asl whose position controls the direction of table grinding wheel is-rotated at high speed in any suitable manner, for instance by a beltdrive, Figs. 3 and 5, for the wheel spindle 10, the said wheel spindlehaving a pulley a which is connected by a belt, not shown, -to a largerpulley 10b that is driven in any suitable manner. The workpiece 6 isalso rotated, but at a slower speed, this rotation being imparted in anysuitable manner, as by a belty drive, not shown, from a countershaft.The machine also embodies the usual instrumentalitiesfor both manual andautomatic cross feed between work and wheel., here shown as embodied ina screw shaft 11 for feeding the wheel head 2 transversely of the table1.4 Said screw shaft 11 may be operated, if desired, by-the usual handwheel 11a.

The lautomatic operation of said screw shaft 11 is eifected in the4usual manner, at each reciprocation of the table 1, by a fixed dog orstop 12 which is engaged by a roller 13 on the end of a pivoted arm 14;the movements of said arm aretransmitted through suitable .pawl andratchet mechanism, not shown, to the screw shaft 11, thereby to obtainthe automatic cross feed of the grinding wheel 5 at each reciprocation'of the table.

All of the above described mechanism .is old and Well known in the art,and of itself forms no part of the present invention. The latter, asclaimed in this particular application, comprises the work gauging orcalipering mechanism and its cooperation' with the other partsjof themachine, the" details of they calipering mechanism beingbest shown inthe detached views of Figs. 6 and 7'. Said mechanism provides a member15, having at one end a work calipering point 16 adapted, during theoperation of grinding a workpiece, to bear against the internal surfacewhich is being ground, and to maintain itscontact with said surface asthe hole in the workpiece is .gradually enlarged by the grinding actionof the wheel. The member 15 is to all intents and purposes a lever, saidmember, for the movement required of it to maintain the point 16 inconstant contact with the interior-ofy the graduallyenlarging hole inthe workpiece, being supported by a pair of flexible U-shaped flatsprings 17 and 18, which springs cross each other, as shown in Fig. 6,and are attached to two adjacent sides of a rectangular block portion 19of member 15. .At 'their other ends the crossed springs 17 and 18 areattached to two inner surfaces 20 and 21 of a box 22, these surfaces 20and 21 being at right angles to each other, and the box 22 providing'anopening 23 of sufficient size to permit the inward extension 15a, ofmember 15, to move freely about'the pivotal axis which is-afforded theintersection of the planes of the U-shaped springs 17 and 18. Thispivotal movementl 1s accomplishedby the iiexing of these two springs,and takes place in the entire absence box 22, is invariably in exactaccordance with the movement of calipering point 16 in maintainingContact with the surface of the gradually enlarging hole in theworkpiece.

Such motion of the member 15 is adapted to be transmitted to anindicator lever 24, pivoted at 25 within the box 22, with its free endadapted to move across the graduationsA of a suitable scale 26. Lostmotion may be eliminated at bearing 25 by a spring 25a. The connectionbetween extension 15a and indicator lever 24 is made by a spring 27,which draws the parts together and maintains the lever 24 in contactwith' the end of a screw 28, said screw being adjustably threaded inextension 15a and passing at its head end through a suitably enlargedslot or hole 29 in box 22, so as to permit adjustment from the exteriorof said box. By turning the screw 28, the indicator lever 24 can be madetov assume any desired position vrelative to the member 15, and saidscrew 2 8 is maintained in any given setting, and displacement thereofprevented by any suitable friction device, such as a spring. 30. Withthe arrangement above described, a

very slight movement of the calipe'ring point.

16 is multiplied many times in being transi mitted to the indicatorlever 24, as will be readily understood.

In the operation of the mechanism, the i calipering point 16 maintainscontact with` the work, the movement of member 15 for this purpose beingobtained bythe pressure of a spring 31, and such movement, greatlymultiplied, being transmitted through the*` above described connections"to the indicator lever 24. The multiplied movement of the latter is madeuse of, at predetermined points, inthe grinding of each workpiece, toset in operation successively, first, the wheel dressinginStruInentaIitieS, and second, the instrumentalities for bringing aboutcessation of .the grinding, -when the workpiece li reaches apredetermined and desired size. To this end, the lever 24 carries twoelectrical contacts, namely a contact 32 for closing an electricalcircuit that controls the wheel dressing operation, and a second contact33 for subsequently closing an electrical circuit that controls theoperations involved in cessation of grinding. In the paths of these twocontacts 32 and 33, the box 22 provides suitable stationary terminalcontacts 34 and 35, respectively. In the movement of lever 24, thepoints 32 and 34 come first into contact, and subsequently the points 33and 35 come into contact; in order to permit this succession ofcontacts, the point 32 which-engages first, is carried by the free 'saidscrew passing through a threaded lug 39 of bracket 37; after the box 22has been adjusted as above described, it is firmly fastened in positionby tightening the bolts 40, 40, which are threaded into the bottom ofthe boX and pass through elongated slots 41, 41 of bracket 37, see Figs.7, 9 and 10. Said bracket 37, which carries box 22, is rigidly attachedt-o the upper end. of a spindle 42, the construction being preferably asshown in Fig. 10, where the bracket 37 seats on a shoulder 43 ofsaidspindle, or on an interposed washer 44, and is held firmly inposition by a nut 45. Below the shoulder 43, the spindle 42 has afrusto-conical poi'- tion 46, the latter being received in a similarlyshaped bearing recess 47 provided by an elongated spindle bearing sleeve48, preferably formed integrally with a casting or bracket 49. Thelatter, as shown in Figs. 1 and 8, is secured to the machine base bybolts 50, which pass through slots 51 of` said casting or bracket, topermit longitudinal adjustment of the same. At its lower end the sleeve48 provides'a ball bearing 52 for the lower end of spindle 42, the outerrace ofvsaid ball bearing being pressed downwardly by a spring 53 andthe inner race being attached to the spindle 42 by a nut 54. See Fig. 7A. capV 55 prevents the entrance of dirt and abrasive to the interiorof'said sleeve.

rlhe above described construction provides an extremelyeifectivemounting for the box 22, to'permit it to swing into inoperativeposition, as shown in Fig. 5, so as to withdraw the calipering point 16from the completed workpiece,prior to the latters. removal from themachine. This swinging movement, on

- account of the extended bearing surfaces surrounding the sleeve 48 and.attached t 46 and 47, takes place in the absence of play or lost motionand is effected in the following manner :*A split collar 56 surroundsthat portion of the bracket 37 which is secured tothe spindle 42, saidcollar being drawn into tight engagement with said bracket by a bolt 57.Extending from said collar is an arm 58 carrying a roller 59 which, inthe normal work engaging position of the calipering point 16, lies inthe path of, but spaced at some distance from, a cam bar 60 attached tothe table 1. In this normal work engaging position, a strong coil spring61,

ere-

to, exerts its force against arm 58 to rotate the lattercounterclockwise. Said arm is firmly attached to the bracket 37 bycollar 56 and bolt 57 and thus the force of spring 61,

exerted on said arm, maintains the calipering and indicating mechanismas a unit in the position shown in Figs. 3, 6 and 8, where a lug 62 onarm 58 brings up against a fixed stop 63 formed on a bracket 63a, whichis attached to the casting 49. At theend of each grinding operation,when the table 1, as hereinafter described, is automatically given anextended movement to the right,

as shown in Fig. 5, the cam bar 60, carried by said table, strikesroller 59and rocks the arm 58 in a clockwise direction, against theforce of spring 61, thereby swinging the entire calipering andindicating mechanism, as a unit, from the position shown in Fig. 3 intothe inoperative position shown in Fi 5, thus allowing thenishedworkpiece to e withdrawn and a new workpiece to be inserted inthe chuckof the work head 3.

Should the operator, for any reason, desire to shift this mechanismmanually into the inoperative position shown in Fig. 5, it is onlynecessary to loosen up on the bolt 57, thereby freeing the bracket 37from the arm 58 and spring 61 and allowing said bracket with theattached boX 22 to be swung freely out of the way. In ,restoring theparts to position for a resumption of the above described automaticoperation, the operator Iswings the'box and bracket until a surface 64on the bracket engages with a lug 65 on arm 58; thereupon, the bolt 57is again tightened to unite said arm and bracket.

In connection with the above described swinging movement of thecalipering and indicating mechanism, the work calipering point 16 isautomatically disposed in a position which prevents it from forciblyengaging the workpiece in the act of entering the same, and which makesit incumbent uponfthe operator to release the member 15, carrying saidpoint, at the commencement of each grinding operation, by movement of ahand lever 66, as will now be described.

A rod 67 having a head 68 provides bearing portions 69 and 70 forsliding movement in bearing holes provided by opposite sides of the box22. Between the bearing portions 69 and 70, the rod has a reduced neck71', forming a shoulder 72 for cooperation with a downward projection73, Fig. 7, of the extension 15a. A spring 74 encircling the rod 67 andthrusting outwardly against the head 68 thereof, draws the shoulder 72against projec-l tion 73, and, in the inoperative position of thecalipering and indicating mechanism shown in Fig. 5, this action ofvspring 74, being stronger than the action of spring 31, rocks the member15 in a clockwise direction, thus to i Vzo swung from the position ofFig. 5 to the position of Fig. 3, the head 68 of rod 67, strikes ahardened'steel stop plate 75 which is secured-to the bracket 63a andthis action forces .the rod 67 inwardly of the box 22 and retionalsafeguard is provided by a shaft 7 6Y which is pivotally mountedtransversely of box 22 in suitable bearings provided by the oppositesides of said box, and which'shaft has secured thereto the hand lever66, hereinbeforerefe'rred to. The disposition of 4said hand lever" issuch that the weight thereot` tends to turn the shaft 76 in a clockwisedirection, viewed from the front of the box 22.l A pin 77 extending fromshaft 76 cooperates with an edgewise shoulder 78 of extension 15a in thefollowing manner When the rod 67, under the influence of spring 74,thrusts outwardly, and thereby rocks the member 15 in a clockwisedirection, the pin 77 moves up in front of shoulder 78, dueto theclockwise rotation of shaft 76 which is brought about b'l the overhangvof hand lever 66. rlhus sai pin 77 serves to ,Llock the member 15 in aposition where the' calipering point 16 will be inoperative. Whensubsequently the head of rod 67 engagesthe stop plate 75 as thecalipering point moves into the work, and relieves the member 15 fromthe iniluence of spring 74, said member, 15 still remains lockedy by pin77 in inoperative position, and is not released from said position untilthe o erator rocks the hand lever 66 upwardly; t ereupon, under theinfluence of spring 31, the calipering point 16 will move into Contactwith the internal surface of the workpiece and the operative connectionbetween extension 15a; and the indicator lever 24 will be established.With the next swinging movement of the parts into the inoperativeposition shown in F ig. 5, the spring 74 moves the member 15 in aclockwise ldirection and the unbalanced weight of handle 66automatically clocks said member in said position. rlhe shaft 76 isadjustable transversely of the box 22 in Order to accommodate theposition of the locking pin 77 to various settings of member 15 fordifferent sizes of work; this is accomplished by an adjusting nut 79 onbearing sleeve 7 9a of said shaft, said nut 79 being held in any desiredsetting by check nut 7 9b.

1nJ the use of the mechanism as described for the quantity production ofidentical workpieces all ground to the exact same internal size, asample piece or pattern is first made and accurately gauged by hand,with the use of the ordinary; sizing plugs or gauges. With this samplepiece at the exact required size, and still rotating in the machine,'after `withdrawal of the grinding wheel from engagement therewith, thebox 22 carrying the calipering and indicating mechanlsm is swung intooperative position,

and the point 16 caused to make contact with the nished ound surface ofthe sample.

VThen with th1s contact gnainta'ined, the position of the box isadjusted so that the end of the lever 24 registers with the zero markingon scale 26, and so that the point 33 on lever 24 will just make contactwith the point l35, the latter being adjustable, in and out,

for this purpose. Under these conditions, the point 32, which is carriedby the spring 36, on lever 24, will also 'be in contact with the point34; that'is to say, the proportions of the parts are such that this lastmentioned contact will have beenmade rst, and will always be made firstin the swingingof lever 24, the spring 36 yielding suiliciently to allowthe'subsequent contact of points 33 and 35 to be made. These settingsofthe calipering and indicating mechanism and of the electrical' contactpoints will -bef maintained throughout the subsequent run of the machinefor the production of workpieces eX- actly like the sample or pattern.

During the normal operation on the workpiece, which is illustrated inFig. 1, the grinding wheel 5 partakes of a longitudinal reciprocatorytraverse, said traverse being iven it by the reciprocations of the table1.

uring said grinding operation the box 22 is in the position illustratedin said gure, and the calipering point 16 on the lever 15 is in contactwith theinternal surface of the gradually enlarging workpiece. Thisgrinding opration continues uninterruptedly until, byoperation of thecallipering and indieating mechanism described, the Contact points 32and 34 are brought together.Y This, by mechanism fully described in saidarent application (Patent No. 1,751,202 a oresaid), causes andamplification of the out,

the grinding wheel 5 is dressed and truedv by a dressing device 133which is lowered into the amplified path of travel of the grlnding wheelcoincident with the said outward movement.

. As shown in the wiring diagram of Fig. 11, eletr'ical currentma'y besupplied bya direct current generator 80, driven continuously, by anysuitable means, not shown, from the same source of power thatY is usedfor the rotation of the grinding wheel or of the work head spindle. @neterminal of this generator 80 is grounded as shown at 81, and the otheris connected by a. supply lead 82 to the central bar or plate 83 of atwo-way switch,-the latter being designatedas a whole by the numeral 84and being disposed as shown in Fig. 1, on the front of themachine. Saidswitch 84 provides additional contact plates or bars 85 and 86, arrangedon opposite sides of the'central barl 83, and adapted to be alternatelyconnected electrically to said central bar 83 by a connector 87 which ismounted on an oscillatory member 88. The latter is pivoted. at 89, andin its full line position as shown in Fig. 11, disposcs. the connector87 in contact with and across the two plates 83 and 86; in its otherextreme position, the movable member 88 of switch 84 disposes theconnector 87. in contact with and across the two pl ates 83 and 85.

The normal position of the movable switch member 88 is that indicatedinFig. 1, and under these conditions, the supply lead 82 from thegenerator '80 is connected to two leads 90 and 91 taken oil' of theplate or bar 85 of the switch 84. One of these leads, 90, runs to thecoil of an electro-magnet 92, disposed on the rear side of the machineand shown in the wiring diagram of Fig. 11. The

return lead 93 from the coil of electromag.

net 92 is connected to the stationary contact point 34 of box 22. Whenthe point 32,

' which is grounded as shown at 94, makes contact with the point 34, theelectrical circuit containing the coil of electro-magnet 92 is closedand said electromagnet is energized. Associated with the electromagnet92 is an armature member 95; energization of .the magnet 92 causesattraction of this armature member resulting in slight oscillation of aspindle 96, which spindle is'vso connected to the dresser movinginstrumentalities shown in plan View in Figs. 3 and 5 that the outwardmovement of the table 1 to behereinafter described will, as a result ofthe oscillation of the said spindle 96, cause the dressing diamond orpoint 133 to be lowered into the path of the grinding wheel, thusdressing and truing the same as shown in Fig. 3. The mechanism formoving the diamond into position is not claimed in the presentapplication, being claimed in a copending divisional @application SerialNo. 181,439, and hence it v will not be described herein; suiiice it ltosay that inthe present embodiment of the invention the energization ofthe magnet 92 is a condition precedent to the energization of anelectromagnet 97 which sets in operation the instrumentalities -causingthe table or carriage 1 to carry the grinding wheel 5 out of theworkpiece for the dressing operation.

The other lead, 91, from switch bar 85 l passes to the coil of theelectromagnet 97,

disposed on the front of the machine, as

r shown in Fig. 1, and the return lead 98 from the coil of electromagnet97 passes to an 1nsulated spring Acontact 99, adjacent to the elec-`tromagnet 92. When the latter, as above described, is, energized by thecontact of points 32-.and 34, the rocking movement of armature vmember95 carries a contact point 100 into engagement with the insulatedcontact 99, and since said contact point 100 is grounded, as shown at101, this grounds and completes the electrical circuit through the coilof electromagnet 97 and energizes said electromagnet. Thus theenergization of the two As shown in Fig. 1, the left hand table dog v 8,which limits the right hand movement of table 1, is carried by a. block144 which, instead of being secured directly to the table 1, as is thecase with the block 145 of doo` 7, is mounted 'so as to be capable ofsliding freely longitudinally of said table. Under normal conditions,when the table 1 is making its usual working reciprocatilons, totraversevthe grinding wheel 5 back and forth within the workpiece, theblock 144 of dog 8' is held in definite spaced relation to a block 146,which latter, the same as the block 145 of right hand dog 7, is astationary block,

A: latch lever 149 pivoted at 150 on the block 146 constitutes the meansto hold the block-144 in spaced relation to the block 146, the righthand bent-over end of 'said lever 149 being normally in engagement witha shoulder 151 provided by the block 144. The eleci tromagnet 97is-located on the front ofthe machine as shown in Fig. 1, and -whenenergized draws downwardly an armature 152 thus rocking upwardly a leverarm 155 carrying a roller 156, these parts being pivoted on a stud orshaft 169. The roller 156 is just below the latch lever 149 and whensaid lever arm 155 and roller 156 are raised in consequence of theenergization of the magnet 97, the latch lever 149 is lifted, thusfreeing it from the shoulder 151. This allows an amplifed movement ofthe table 1, for the reason Vthat the block 144 is not now rigidlyattached to said table but is slidable thereon, and therefore the dog 8will not immediately shift the reversing member 9, the resistance ofsaid reversing member being greater than the friction of the slidableblock 144 on the guideways by which it is carried on the table 1.Ultimately, however, the block 144 is engaged by the rigidly attachedblock 146 and thereupon the dog 8, being thus backed up, shifts thereversing member 9 and the table 1, then moves again to the left tocarry the grinding wheel 5 into the rotating workpiece 6. By such returnof the table the block 144 is repositioned with the latch lever 149again behind the shoulder 151. This repositionino' means is fullydescribed in the said may be dressed and trued by the dressing devicewhich is lowered into position as already set forth, followed bysubsequent resumption ofthe normal reciprocatory traverse between wheeland workpiece.

Repetition of the amplified dressing stroke is prevented, despitemaintenance of the contacts 32 and 34 together, by the followingmechanism. On the amplified outward or right hand stroke of the table 1,an outwardly land downwardly projecting bar 163, pivotsecured to theblock 146 that moves 1n.

all

unison with the4 table, strikes an arm 164, Figs. 1 and 11, of movableswitch member 88, thereby rocking said member from the posltion shown inFig. 1 to the position shown 1n Fig. 1 1, where the connector4 87 nolonger makes contact with the right hand swltcll' barA 85. Thisterminates the supply of current toV the electromagnets 92 and 97, sothat,

notwithstanding the continued contact between the oints 32 and 34, therespective armatures e -said magnets are rendered free-to move bygravity to their normal inoperative positions. Thereupon, 'the grindingwheel 5 having returned to its position of normal traverse in theworkpiece 6, as illustrated in Fig. 1, the. grinding of said workpieceis cgntinued without further interruption for dressing despite .themaintenance of the `aforesaid centactA by the calipering mechanism.

It should be noted that the amplified motion given to the table 1 asjust described do's not move it far enough to cause the cam bar 60 tocontact with the roller 59, so that thev box 22 and consequently thecalipering lever v15 and point 1.6 remain undisturbed.

Subsequent to this dressing operation, the normal grinding traverse isresumed until, by the making of the contacts 33 and 35 under thecontrolLof the calipering mechanism, the table 1 is caused to withdrawto the extremeposition of Figs. 4 and 5 thus definitely terminating thegrinding operation on that particular workpiece. This extended travel ofthe table 1 is brought about in the following manner Again referring toFig. 11, the left hand bar or plate 86 of the switch 84'is connected bya lead or conductor 165 to an electromagnet 166.. The other terminal ofsaid electromagnet 166 is connected by a lead 1'67 to the contactyterminal 35. Subsequent to the dressing operation briefly described, the'connector 87 on the oscillatory member 88 provided by the switch 84occupies the position shown in Fig. 11, connecting together the platesor bars 83 and 86,' and thus when the terminals- 33 and 35 come'togetherthe electric circuit is completed through the elecmagnet 97 `in Fig. 1.The electromagnet 166 h as associated therewith an armature member 168and a lever arm 171, both being integrally connected and being pivotedabout the pivot shaft 169. The lever arm 171 may be clearly seen inFigs. 1, 2 and 4; it lies vin the same vertical plane as, and normallyjust Abelow,'the table controlling dogs. The

dog 8 is a pivotally mounted dog and when, by reason of the attractionof the armature 168 responsive to energization of the electromagnet 166,the lever arm 171 is raised, the free end of said dog, on the righthandmovement of thetable 1, engages with and rides upon the lpwa-rdlyinclined surface of arm 171 and is thus carried clear of the reversingmember 9.7 Thus ysaid table 1, through the disposal of dog 8 in a whollyinoperative position, continues its movement to the right, carrying thegrinding wheelv 5 out of the workpiece 6, said table finally beingbrought to a full stop in the position of Figs. 4 and 5 by any suitablemeans, such as that disclosed inthe aforesaid Guild. .Y Y

This extended travelof the table 1, as already stated, brings the cambar 60 into contact with the roller 59 provided by the depending arm 58,thus rocking the calipering' box 22 to the position shown in Fig. 5 andsetting in operation the instrumentalities for locking the calipermember 15 in the inoperative position. k

From the foregoing it will be seen vthat we patent to Heald. and

- have, provided avery effective mechanism for llO controlling adressing operation to take place 'duringthe operation on a workpiece andfor )causing the grinding' operation to cease and determine when theworkpiece reaches the desired size, the control being obtained by directcontact with the gradually enlarging hole in the workpiece. Furthermore,,our invention provides a mechanism that is easily adjusted fordifferentsizes of workpieces,

and the calipering element of our mechanism ismade to readily enter andleave a workpiece without disarranging the adjustments and withoutchipping the dia-mond contact point that is preferably used.

2. In an internal grinding machine, a work calipering mechanismproviding a calipering member having a calipering point that makescontact, during the grinding operation, with the surface of the hole inthe workpiece, means for moving said calipering member to carry' saidpoint out of the hole, means set in operation by said movement formoving said point to an inoperative position, and means for locking itthere.

3. Inl an internal grinding machine, a work calipering mechanismproviding a caliper.- ing member having a calipering point adapted forcontact, during the grinding operation, with the surface of the hole inthe Workpiece, said mechanism being movable toward and away from saidhole, and means operated in response to such movements of said mechanismfor maintaining said point out of con-J tact with the workpiece duringthe passage of said calipering member into and out of said hole.

4. In an internal grinding machine, a work calipering mechanism'providing a calipering member having a calipering point adapted forcontact, during the grinding operation, with the surface of the hole inthe workpiece, said mechanism being movable toward and away from saidhole, locking means operated by such movements of said mechanism forholding said point in an inoperative position during the passage of saidcalipering member into and out of said hole, so as to prevent chippingof said point, and manually controlled means for releasing said lockingmeans.

5. In a grinding machine, a work calipering mechanism movable into andout of operative relation to the work, a inding wheel having areciprocatory wor ing traverse relative to the work, and meansresponsive to an increase of said traverse for procuring the movement ofsaid calipering mechanism into inoperative position.

6. In a grinding machine, a work calipering mechanism movable into andout of operative relation to the work, a grinding Wheel, Kmeans forwithdrawing said wheel from said work into dressing position withouteffect on said work calipering mechanism, and means, responsive to afurther withdrawal of said grinding wheel, for procuring the movement ofsaid calipering mechanism into inoperative position.

7. In a grinding machine, a work calipering mechanism movable into andout of operative relation to the work, a grinding wheel having areciprocatory working traverse relative to the work, means for-increasing said traverse to subject said wheel to a dressing operation,without eifect on said work calipering mechanism, and means forprocuring the movement of said calipering mechanism into inoperativeposition on a further increase of said traverse.

8. In an internal grinding machine, a work calipering mechanism having awork calipering point mounted so as to be movable in the operativeposition of said mechanism, substantially radially toward and fromthesurface of the hole in the workpiece, said mechanism being movable tocarry said point into and out of said hole, a positive stop `forlimiting the inward movement of said mechanism, resilient means forholding said point out of contact-with the work during movement intosaid hole, and means acting against said resilient means to release saidpoint'upon engagement of said mechanism with said positive stop.

9. In an internal grinding machine, a work calipering mechanismproviding a calipering member having a calipering point adapted to makecontact, during the grinding operation, with the surface of the hole ina workpiece, means for moving said mechanism to carry said caliperingpoint into and out of said hole, means responsive to such movements forautomatically retracting said point, so as to prevent contact with saidworkpiece, during the movements of said calipering mechanism whichcarries said point into and out of said hole, and locking means forholding it there.

10. In an internal grinding machine, a Work calipering mechanismproviding a calipering member having a calipering point adapted to makecontact, during the grinding operation, with the surface of the hole ina. workpiece, means for moving said mechanism to carry said caliperingpoint into and out of said hole, means responsive to said movement forautomatically retracting said point, so as to prevent contact with saidWorkpiece, during the movements of said calipering mechanism whichcarries said point into and out of said hole, means for locking saidpoint in said retracted position, and means for freeing Said point fromsaid locking means, to permit contact with the surface of said hole,after said calipering mechanism has been moved to dispose said pointwithin said hole.

11. In an internal grinding machine, a work calipering device, asupporttherefor, a movable arm provided by said device, means for moving saidsupport to carry said arm out of the hole in a workpiece, resilientmeans for movin said arm relative to said device to permit t e arm to becarried out of the hole without touching the mo'uth thereof, means formoving said support to carry the arm back into the hole, and a stopadapted to be Y contacted by said resilient means, whereby the meanscausing return movement of the support resets the resilient means, thusto permit the arm to be restored to its normal position relative to thedevice in order to caliper the workpiece.

12. In an internal grinding machine, a. work calipering device, asupport therefor, a movable arm provided by said device, means formoving said support to carry said arm into the hole in a workpiece, astop cooperating with said support to limit the movement of said varminto said hole, means for moving said support to carry the arm out ofthe hole, resilient means for moving said arm relative to said device topermit the arm to be carried out of the hole without touching the mouththereof, and a stop adapted to be contacted by said resilient means,whereby the means causing return movement of the support resets theresilient means, thus to permit the arm to be restored to its normalposition relative to the device in orderto4 caliper the workpiece.

13. In an internal 4grinding machine,v

mechanism for calipering the hole of a workf piece in said machine, saidmechanism including a movable arm having a calipering point forengagement with the surface of. said hole, means :for moving saidmechanism to carry said point into and out 'of said hole,

- and means brought into operation by such movements of said lmechanismfor shifting said arm relative to said mechanism, thereby to preventengagement of said point with the mouth of said hole vwhile saidmechanism Ais in motion.

BGG-ER N. HEALD. WALDO d'. GUILD. ALFRED l?. BURNS. GEORGE E. GARN.

